Venovenous Bypass

Another extracorporeal technique used in certain special situations is venovenous bypass (VVB). It is used predominantly for vascular isolation of difficult inferior vena cava procedures. VVB was originally described for the anhepatic phase of liver transplantation. Other uses include the resection of renal and adrenal tumors with caval involvement and trauma to the retrohepatic inferior vena cava. VVB drains blood from the lower half of the body via a centrifugal pump into the central venous circulation. The systemic inflow into the circuit is from the femoral vein and the outflow is either the right atrium or axillary vein (Fig. 3.5). The portal system can be drained with a separate cannula into the inferior mesenteric vein. Flows are in the range of 2-3 l/min and because there is no oxygenator in the circuit, the blood remains deoxygenated. Heparinization is usually in the range of 100 units/kg, although cases have been successfully done without systemic heparin.

Clamping the inferior vena cava leads to rapid central hypovolemic shock because of sequestration of blood in the lower extremities without return to the heart. VVB allows for vascular isolation of the inferior vena cava with continued return of lower extremity venous blood to the heart. Drainage of the portal system into the VVB circuit prevents the accumulation of toxic gut metabolites which may be arrhythmogenic when the cross-clamps are released. The complete VVB circuit is shown in Figure 3.6 for resection of a right renal cell carcinoma involving the cava. It is important to recognize that if the tumor thrombus extends up into the right atrium, VVB is no longer technically possible because snare control of the intrapericardial inferior vena cava will trap and break off the tumor. To resect such a tumor, it may be necessary to establish full cardiopulmonary bypass, cool to profound hypothermia, and establish circulatory arrest. Figure 3.7 depicts such a tumor requiring circulatory arrest for resection.

Axillary Femoral Bypass Pump

Fig. 3.5. Schematic diagram of VVB. Systemic blood is actively drained from the femoral vein via a centrifugal pump to the central venous system. Portal decompression may be achieved via the inferior mesenteric vein.

Fig. 3.5. Schematic diagram of VVB. Systemic blood is actively drained from the femoral vein via a centrifugal pump to the central venous system. Portal decompression may be achieved via the inferior mesenteric vein.

Fig. 3.6a. CT scan of a right renal cell carcinoma with tumor extending up the inferior vena cava.

Fig. 3.6b. The venovenous bypass circuit drains femoral venous and portal blood into the right atrium. Vascular control of the infrarenal cava, intrapericardial cava, right renal artery, left renal vein, hepatic artery and portal vein is shown.

Fig. 3.6b. The venovenous bypass circuit drains femoral venous and portal blood into the right atrium. Vascular control of the infrarenal cava, intrapericardial cava, right renal artery, left renal vein, hepatic artery and portal vein is shown.

Venovenous Bypass
Fig. 3.7a. Right renal cell carcinoma growing up the inferior vena cava into the right atrium. Cardiopulmonary bypass, profound hypothermia and circulatory arrest are required for resection of such a tumor.
Cannulas For Venoveno Bypass
Fig. 3.7b. Example of a renal cell carcinoma resected with this technique.

Suggested Reading

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  • SELINA GAMMIDGE
    How to perform venovenous bypass?
    6 years ago

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